Dietary tea polyphenols induce changes in immune response and intestinal microbiota in Koi carp, cryprinus carpio

We evaluated the effects of dietary tea polyphenols (TP) on growth, immune response and intestinal bacterial community in Koi carp (cryprinus carpio). One hundred and eighty fish were randomly assigned to a basal diet or three treatments consisting of basal diet supplemented with three dosage of TP. Body weight were measured at the beginning and end of trial. Blood and intestinal samples were collected at the end of trial to determine immune response and intestinal bacterial community. The results indicated that lipase activity increased in the TP-500 and TP-1000 treatments (P = 0.0007). Dietary TP decreased the concentration of serum IL-1 IL-6, lysozyme, complement C4 and C3 (P < 0.0001; P < 0.0001; P = 0.0007; P < 0.0001; P = 0.0365, respectively). No differences was observed in the body weight, protease and amylase activities, and serum TNF-alpha among the treatment and control groups. Proteobacteria was more abundance in the TP-500 and TP-1000 treatments compared to that in control (P = 0.0346; P = 0.0005), whereas Fusobacteria was less abundance in the TP-1000 treatment (P = 0.0008). Intestinal bacteria, indicated by simpson and shannon indices, was more diverse in the TP-1000 treatment. The principal coordinate analysis (PCoA) based on weighted UniFrac distance indicated that bacterial community of the TP-1000 or TP-500 treatment was separated from that of control (P = 0.001; P = 0.008). In conclusion, dietary supplementation of TP had anti-inflammation effects, but attenuated non-specific immune response. These TP-mediated changes in immune response may be associated with the structure of intestinal bacterial community.